The following text is taken from articles in the EMPO Times, EMPO's newsletter. It is designed to provide introductory information for the new ski-orienteer.
Ski-Orienteering is orienteering. This may seem obvious to you, or it may seem crazy. Here in Upstate New York there are many, myself included, who actually started orienteering on skis and only later moved to the running-through-the-woods version. (I won't call it "Foot-O" because so many people, mostly non-skiers, object to that term. And since your feet are also involved in Ski-O, while connected to your skis, I think they have a point.) Regardless, what makes Ski-O a true form of "O" is the essential ingredient of route choice.
Ski-O courses are set such that the controls are along trails, much as they are for White courses during the non-ski seasons. But there are some critical factors, which need to be taken into account on a Ski-O course, that few White course runners would consider. First there is elevation change. While the "going over vs. going around" choice is a classic orienteering decision, in Ski-O it is exaggerated because the difference between skiing uphill and on the flat is much greater than the difference when running. Plus, even the downhills can be problem when skiing, because the speed you develop can require extremely fast decisions and very technically difficult turns. There are few things more frustrating than realizing you have missed a turn you needed to make and must climb back up several hundred meters.
Secondly, there are track differences, the effects of which are heightened by equipment choices. There is no doubt that once you have mastered the technique, Skating is a faster way to ski than Classic. Skating is not always viable option, depending upon the snow and track conditions, but even where you can skate much of the course, a good course setter will throw in some narrow tracks and bushwhack options, which will be impossible to skate. So, do you go around on the wide track, skating all the way; wind through on the narrow track, double poling if you're using skate skis; or break new trail bushwhacking as straight as you can to the flag?
Through trial and error, and keeping some logs, I've developed a rough guide for making these choices, for myself. Factors which may throw these calculations off include: snow depth, crust support, undulation of terrain, your relative prowess in skating or classic, the alignment of the stars, wax, streams to cross. Over a short distance (less than .5k) skating has a 150% advantage over double poling along a narrow track. Thus, if it's 300 meters to skate to the control, and 100m to double pole, then pole away. But if it's 250m to skate, and 200m to pole, then skate around. The longer the distance, the greater the advantage to skating.
Even tougher is the choice of when to bushwhack. Skating skis simply aren't made for it, and even classic skis can get hopelessly bogged down in deep snow. Here my rough guide is that skating has a 300% advantage, and it's often even more when there is any undergrowth showing through the snow (as with icebergs, 67% of the danger is below the surface). Nonetheless, bushwhacks often look tempting, and succeeding with them can be the difference allowing you to outpace someone who is faster pure skier than you are. So look for them, but look carefully. And the shorter and flatter they are, the more viable they are. For uphill bushwhacks, you frequently want to just take your skis off and carry them, so you have to factor in some time to get them back on again. And beware of streams. I once took my skis off to cross a small stream, and then couldn't get the ice out of the binding slots in my boots for ten minutes. Think ahead!
So, while Ski-O may seem "simple" to the run-only types, it too is a complex route choice decision process. Plus it's usually done at higher speed, and it's definitely done at much closer to (my) exhaustion point. Remember Platt's dictum: if it's too easy, you're not running (or skiing) fast enough!
Are these ideas clear? If not, then ask another experienced orienteer at the next Meet you attend to explain them better. Everyone has different ways of thinking about these things, and someone else's may click better with you.